I've been doing cardio for years and I'm pretty "die-hard" at it. Not only do I train at a high intensity, but I also go for the length of the workout. For some reason, I've always had it in my head that I need to do cardio for at least 60 min. and that's what I've been doing all along. My workouts usually happen 3-5 times a week (I often *aim* for every day in the week, but it's simply not realistic, I suppose, due to time and physical endurance constraints).
Sometimes I feel so overwhelmed with the amount of cardio training I force myself to do that I often get into the all-or-nothing thinking and don't do it at all. I realize that it's better to do even 20 min. than nothing, but when I'm at the gym, if I stay on a machine for only half an hour, I really feel that I shouldn't have come at all and that I might as well make it a whole hour so that it counts for something. The amount of calories burned in half an hour, it seems, is negligible and the fat burning, from what I understand, does not even begin before 20 min. Even regardless of this (I'm not trying to lose weight per se, though I wouldn't mind getting my body fat percentage down. I just want to keep fit and prevent weight gain), I want to train for endurance and it seems that I need to prove to myself that I can keep going for at least an hour, otherwise I'm a failure.
Anyway, my point is that I don't always have the time and the energy (mental or physical) to train for a whole hour. In addition to stretching, ab work, and sometimes some sauna/steam room time, this takes up a good two hours of my time, which is quite a bit, especially after a long day at work. The time limit on cardio machines at my gym is 30 min... I know most people only do that much cardio. I'm wondering if anyone has had any weight loss and general fitness success by doing cardio training for only half an hour at a time. I realize it would have to be combined with weights, which I already do, but not often enough, since cardio always takes priority with me... It's probably all in my head but I have a love-hate relationship w/ it and I can't live w/o it...
Please feel free to share your experiences and provide some specific examples, numbers, etc.